Ovulation rate, zygote recovery and follicular populations in FSH-superovulated goats treated with PGF_2α and/or GnRH

Follicular development and ovulation were examined in superovulated Nubian and Nubian-cross dairy goats following prostaglandin F_2α (PGF_2α) and/or gonadotropin releasing hormone (GnRH) treatment. Estrus was synchronized with Synchromate-B^® implants. Superovulation was induced with follicle stimulating hormone (FSH) and augmented with GnRH and/or PGF_2α. The PGF_2α treatment was administered on Day 2 of superovulation. Implants were removed from all goats on Day 3 of superovulation. The GnRH treatment was administered 24 h after implant removal. All does were exposed to fertile males for 48 h at the time of GnRH injection. Surgical embryo recovery and ovarian response evaluation were conducted 64 to 78.5 h after implant removal. The number of ovulations was higher with GnRH treatment (18.5 ± 7; x ± SEM) than that in the controls (5.3 ± 4.1; P < 0.05). There were fewer follicles in the GnRH-treated does than in the untreated does (10.9 ± 2.9 vs 22.1 ± 3.2; P < 0.05). The number of follicles smaller than 4 mm in diameter (5.8 ± 0.8) did not differ between treatments. The GnRH-treated does had fewer 4- to 8-mm follicles (4.2 ± 2.0 vs 9.1 ± 1.6; P < 0.05) and fewer follicles larger than 8 mm (0.7 ± 1.4 vs 7.3 ± 1.6; P < 0.01) than the controls. Predicted times for 1- and 2-cell embryo recoveries were 68.5 and 73.7 h following implant removal, respectively. This study demonstrates that GnRH is an effective supplement used with FSH superovulation regimens in dairy goats. Moreover, GnRH provides for enhanced early embryo collection for DNA microinjection studies.